The oxygen equilibrium curve of fetal blood is a major determinant of tissue oxygen tension and thus of oxygen supply to fetal tissues. The harmful effects of carbon monoxide on the fetus derive from its effect on the oxygen binding properties of fetal hemoglobins. Despite the great clinical importance of this area, oxygen binding properties of fetal blood currently are known only at one point on the curve, i.e., the affinity at half-saturation, P50. Direct measuremnt of carbon monoxide affinity and especially of carbon monoxide's effect on oxygen binding are not known for fetal blood. Fetal respiratory gas equilibria are more complicated than in the case of adult blood because the fetus has several hemoglobins of diffeing ligand binding affinity and the proportions of these hemoglobins, Hb F, Hb F1 and Hb A, change with gestational age. We will apply new methods toward investigating these key equilibria. The affinity of fetal and neonatal blood for oxygen, carbon monoxide and for oxygen in the presence of carbon monoxide will be measured. These measurements will be carried out by a recently developed micro blood-film technique for measuring the complete dynamic ligand equilibrium curve from zero to complete saturation. In addition the interaction coefficients for protons, carbon dioxide and diphosphoglycerate (DPG) for each of the ligand equilibrium curves above will be sought. Affinities and interaction coefficients will be determined at all saturations. All measurements will be made on blood whose isohemoglobin profile has been established by isoelectric focusing. The goal of this work is to synthesize the results of these measurements into clinically useful practical nomograms describing oxygen transport in the presence and absence of carbon monoxide in normal fetal and neonatal blood.